White crystal aggregates of the very rare mineral lokkaite-(Y) from Norway (Kilebygd, Skien, Vestfold og Telemark, Norway). Lokkaite-(Y) is a Gadolinium (Gd) and also a Dysprosium (Dy) mineral. Gd and Dy are extremely rare chemical elements in minerals, since only 4 mineral species of a total of more than 5700 mineral species known have Gd and Dy in its chemical composition. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Lokkaite-(Y)
Lokkaite-(Y) is an IMA-recognized mineral species in the carbonate class, with the chemical formula CaY₄(CO₃)₇·9H₂O.
It crystallizes in the orthorhombic crystal system. It is a member of the Tengerite structural group.
Key properties: specific gravity 2.92; optically biaxial.
IMA symbol Lok-Y, IMA status: approved, named in 1969.
Forms secondarily through alteration of primary rare-earth minerals.
It is found associated with Tengerite-(Y) (Pyörönmaa pegmatite, Finland); lanthanite, kimuraite-(Y) (Kirigo, Japan).
The mineral was named to honor Professor Lauri Lokka (1885–1966), Finnish mineralogist and Chief Chemist, Geological Survey of Finland, Helsinki, Finland.